Beyond standard photo-electric infrared beams, arcade game mechanics rely heavily on Proximity Sensors and Rotary Encoders to detect mechanical positions, coin drops, motor rotations, and physical player movements.
Understanding these components ensures fast diagnostic turns when servicing complex arcade attractions such as ticket redemptions, coin pushers, and carnival-style physical games.
- Proximity Inductive
- Proximity Capacitive
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| Proximity Inductive |
What is a Proximity Sensor (Proximity Switch)?
A Proximity Sensor (or Proximity Switch) is a non-contact detection device that senses the presence or absence of an object when it enters a specific detection zone.
Key Characteristics:
Short Sensing Range: Operates at very close range—typically from 1 mm up to a few centimeters, depending on the sensor model.
Operating Voltage: Standard industrial/arcade variants operate on 10–30 VDC, though high-voltage models operating on 100–200 VAC also exist.
Non-Contact Operation: Prevents mechanical wear and tear, making it ideal for high-vibration arcade environments.
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| Proximity Capacitive |
Types of Proximity Sensors Used in Arcades
Proximity sensors are categorized based on the physical properties of the materials they detect:
+-----------------------------------+
| PROXIMITY SENSORS |
+-----------------+-----------------+
|
+-------------------------+-------------------------+
| |
v v
[ INDUCTIVE PROXIMITY ] [ CAPACITIVE PROXIMITY ]
• Detects: Ferrous Metals (Iron/Steel) • Detects: ALL Materials (Metal, Plastic,
• Ignores: Non-metal obstacles Wood, Liquids, Glass, Rubber)
• Arcade Apps: Firefighter, Dino Time • Arcade Apps: Street Basketball, Jungle
Bowling, Disco Winner
1. Inductive Proximity Sensors (Metal Detection Only)
Inductive proximity sensors generate an electromagnetic field at their sensing face. They exclusively detect ferrous metal/iron targets.
Key Feature: If a non-metal object (like plastic, wood, or cardboard) blocks the sensor, the sensor ignores it and continues detecting metallic targets behind or through the barrier—as long as the target stays within the maximum sensing range.
Common Arcade Applications:
Firefighter: Detecting metal lever position or nozzle movement.
Dino Time: Tracking metallic gear alignment, target flaps, or mechanical coin-drop gates.
2. Capacitive Proximity Sensors (Universal Target Detection)
Capacitive proximity sensors measure changes in an electrostatic field. They detect all object types, including metals, plastics, liquids, glass, and wood.
Key Feature: High sensitivity to any dense material passing through its close-range envelope.
Common Arcade Applications:
Street Basketball: Rim-mounted ball passage detection.
Jungle Bowling & Disco Winner: Ball track positioning, plastic target flips, or coin distribution detection.
How to Test and Diagnose Proximity Sensors
You can verify whether a proximity switch is working properly using two practical methods: LED Indicator Visual Inspection or Multimeter Voltage Measurement.
Method 1: LED Indicator Visual Test
Most proximity sensors feature an integrated LED status light on the rear housing:
Active-High / Normally Open (NO) Configuration:
No Target (OPEN): LED is OFF.
Target Present (CLOSED): LED turns ON.
Active-Low / Normally Closed (NC) Configuration:
Target Present (CLOSED): LED turns OFF.
No Target (OPEN): LED turns ON.
Diagnostic Rule: Bring a metal target (for Inductive) or any solid object (for Capacitive) near the sensor face. If the LED toggles cleanly between states, the internal sensing circuit is functioning correctly.
Method 2: Multimeter DC Voltage Test (Signal Pin to Ground)
For deeper troubleshooting when the LED lights up but the main game board still fails to register input:
[ Power Source: 12V / 24V DC ] --------> (VCC Pin - Brown Wire)
[ Ground / Com ] ----------------------> (GND Pin - Blue Wire)
[ Multimeter (+) Probe ] --------------> (Out / Drive Pin - Black or White Wire)
[ Multimeter (-) Probe ] --------------> (GND Pin - Blue Wire)
Supply standard working power (10–30 VDC) to the sensor power wires.
Set your digital multimeter to DC Volts ($V_{DC}$).
Place the red probe on the Signal Output Pin (Drive/Out) and the black probe on Ground (GND).
Observe the voltage response:
State 1 (OPEN): Reads approximately 5V DC (or VCC voltage depending on pull-up logic).
State 2 (CLOSED): Voltage drops to 0V DC.
If the output voltage switches between 5V and 0V cleanly upon bringing a target near, the sensor signal driver is healthy.
Other Essential Arcade Sensors: The Rotary Encoder
While proximity sensors handle basic proximity and position switching, Rotary Encoders (Rotary Sensors) measure continuous mechanical rotation, velocity, and angular direction.
+--------------------+
| ROTARY ENCODER |
| (Optical / Magn.) |
+---------+----------+
|
[Rotating Shaft]
|
+----------+----------+
v v
[PULSE GENERATION] [POSITION & SPEED]
Pulsed signals (A/B) Calculates exact wheel
sent to game board angle and spin speed
How Rotary Encoders Work in Arcades:
Rotary Shaft: Connected directly to steering wheels, ticket wheels, or motor spindles.
Pulse Signal Output: As the shaft spins, the encoder outputs digital pulse trains (Phase A & Phase B signals).
Game Logic: The game board counts these pulses to calculate exact steering angles, wheel spin speeds, or physical ticket distribution counts.
Primary Arcade Applications:
Racing Games: Steering wheel orientation and force-feedback centering (e.g., Mario Kart Arcade GP, Initial D).
Wheel of Fortune / Spinner Games: Measuring spin strength, speed decay, and winning segment position (e.g., Big Bass Wheel, Spin-N-Win).
Ticket Dispensers: Precision counting of physical ticket notches as they pass through the dispenser rollers.
Summary: Quick Sensor Reference Guide
| Sensor Type | Target Material | Sensing Distance | Primary Arcade Role |
| Infrared (IR) Beam | Any opaque object | Up to 1–2 meters | Ball scoring, hoop tracking (Dream Shooter) |
| Inductive Proximity | Ferrous Metals Only | 1 mm – 10 mm | Mechanical home positioning, metal gates |
| Capacitive Proximity | Any Solid / Liquid | 1 mm – 20 mm | Plastic ball detection, non-metal targets |
| Rotary Encoder | Physical Shaft Rotation | Continuous ($360^\circ$) | Steering, spinner wheels, ticket counting |
